The present invention relates generally to sensors and more particularly to a sensor that is calibrated automatically. Known sensors are used to detect the rotary movement of valves or motors used in an industrial process, whereas other known sensors are used to detect the linear movement of doors, windows, etc.
Known sensors require manual adjustment or calibration to ensure that the sensor is properly positioned with respect to the object being sensed so that the sensor gives the desired output when the object being sensed is in a certain position. Typically, calibration of known sensors is accomplished using either an inherent calibration method or a measurement and adjustment method. For example, to utilize the inherent calibration method, the conventional sensor is fabricated to include various positioning features such that, when the sensor is coupled to the object being sensed, the positional relationship between the sensor and the object being sensed is sufficiently accurate without any further adjustment. The second method, measurement and adjustment, may be accomplished by positioning the sensor so that the sensor and the object to be sensed are in contact. The sensor is then adjusted until the sensor's desired output is obtained at this predetermined position. Optionally, the sensor is set to the desired output and the sensor is repositioned to ensure that it is in contact with the object to be sensed.
The above described sensors and methods of installation each require that an operator have sufficient manual dexterity to position the sensor. The known sensors may also require that an additional device, e.g. a spacer, be installed to position the sensor. Known sensors also require the operator to have sufficient knowledge and tools or instruments to measure and adjust the sensor to achieve the desired output for a given position.
Thus, a need exists for an improved sensor that is accurate, consistent, and operates with minimal opportunity for human error. Preferably, such a sensor permits calibrating the physical relationship between the object to be sensed and the sensor without using any tools. Additionally, a need exists to provide a sensor that may be installed and calibrated in a shorter period of time than other known sensors allow, and to enable the operator to install the sensors with relatively little training. A need also exists for a sensor that permits easy and quick visual verification that the sensor has been calibrated.